Some migrants have a number in black ink written on their arms. Here’s why.

To some, the thought of asylum-seekers on the U.S.-Mexico border with numbers written in black ink on their arms carries disturbing echoes of the Holocaust.

But to Michael, a 43-year-old migrant who says he left Cuba one year ago, the black ink represents a shot at a new life. And on a practical level, it represents his place in line at the border.

“I hope that yes, with these numbers I will get to the border there and that everything will turn out good.”

Congressman Beto O’Rourke brought attention to the numbers in a video he shared on Twitter on Friday. In the video, he speaks to two asylum-seekers in the U.S.-Mexico border city of Juarez with numbers written on their arms.

Visited Juárez to hear directly from asylum seekers. Met one mother who traveled from Guatemala with her 10-year-old daughter. It took them more than 3 weeks to arrive here. Their place in line to petition for asylum is now written on their arms with a marker: 2142 & 2143. pic.twitter.com/TyVKoF3v50

The video garnered more than a million views and outraged comments, many directed at the Trump administration. But officials on both sides of the border said the U.S. and Mexican governments are not responsible for the numbers.

It’s hard to track down the origin of the system, but it appears to have been created as an unofficial waitlist. Gabriel Reyes with the Mexican Red Cross in Juarez told CNN that the system was created a few weeks ago to get migrants off the bridge and into shelters, and that migrants themselves wrote the numbers on their arms as a way to prove their place in line for processing.

A DHS official said US authorities are not marking any migrants with numbers.

A representative of advocacy group Casa del Migrante told CNN that the numbers create order for migrants. Staff and volunteers with Casa del Migrante offer migrants the option of writing down their number on a slip of paper or on their arm so they have their number.

The written numbers struck a chord with those who oppose the Trump Administration’s crackdown on immigration and asylum-seekers.

During World War II, prisoners who arrived at Auschwitz were tattooed with a serial number so officials could identify those who died. The numbered tattoos have become some of the most prominent and easily visible evidence of the dehumanization of Jewish and other minority prisoners during the war.

In O’Rourke’s video, he said that the woman and her 10-year-old daughter arrived from Guatemala and were seeking asylum in the United States.

O’Rourke said that the woman said she had traveled for three weeks to get to Juarez and that she was trying to lawfully petition for asylum. The numbers written on their arm – 2142 and 2143 – are in ink and are not tattoos.